Sound reproducing apparatus



July 26, 1932. E. PODSZUS SOUND REPRODUCING APPARATUS Filed June 19.1930 INVENTOR Attorney.

' telephone receiver,

Patented July 26, 1932 UNITED STATES PATENT OFFICE SOUND REPRODUCINGAPPARATUS Application filed June 19, 1930, Serial No. 462,332, and inGermany June 26, 1929.

device. My improved checking means are useful in sound reproducingapparatus of any type comprising a diaphragm and particularly inapparatus provided with a comparatively rigid diaphragm of highelasticity, such as telephones and the like. For checking the saidnatural vibrations of the diaphragm I apply thin checking members tothose points of the diaphragm where they are adapted to checkparticularly the overtones of the natural vibrations of the diaphragm,while they do not interfere with the vibrations imparted to thediaphragm by the sound reproducing device by reason of their thinconstruction and proper distribution on the diaphragm, so that theyinsure correct reproduction particularly of the sounds of high frequencywhich are essential in reproducing sounds in the correct timbre.

For the purpose of explaining the invention an example embodying thesame has 5 been shown in the accompanying drawing in which the samereference characters have been used in all the views to indicatecorresponding parts. In said drawing,

Fig. 1 is a sectional elevation showing a Fig. 2 is a sectionalelevation taken on the line 22 of Fig. 1,

Fig. 3 is a sectional elevation on an enlarged scale showing theconstruction of the checking members, and

Fig. 4: is a side view of Fig. 3 with the disk closing the telephonereceiver removed.

In the example shown in the drawing the sound reproducing devicecomprises a box 0 having a diaphragm b fixed thereto by means of a diska carrying a tubular member 61. Through holes 6 made in the bottom ofthe box a the cores 7 of an electromagnet g are passed into position foracting on the diaphragm. V y

The diaphragm b is acted upon by checking members made in the form ofexceedingly thin wires it having a thickness of say 0,018 millimetersand made from tungsten, steel or other material of high elasticity, thesaid wires being in contact with the bottom of the box a and the disk 0,which bottom and disk are preferably disposed at a distance of from 1-2millimeters away from the diaphragm. The said wires are bent into curvedor other irregular shape, and in the example shown in the figures theyare in the form of line coils or curved springs and they are in pointcontact with the diaphragm. They may be in loose engagement with thediaphragm, but I prefer to fix the same to the diaphragm by means oflacquer or glue for securely coupling the same with the diaphragm in thedesired positions.

The said checking members are exclusively applied to the points of thediaphragm corresponding to the loops of the overtones of the naturalvibrations of the diaphragm, and

their number and power are such that they take up the increase of theamplitude of the desired vibrations caused by the natural vibrations ofthe diaphragm in case of median excitation thereof, and therefore theyare dif ferent in size and thickness according to the intensity of thevibration to be checked. Preferably I use a diaphragm having acomparatively low natural frequency because in such a diaphragm thehigher tones are more readily excited in a regular way.

The elastic reaction of the checking members depends on their number, onthe thickness and the curvature of the wire, and the character of thematerial. It is not neces: sary to apply checking members to all theloops of the natural vibrations of the diaphragm, or to apply suchchecking members to all the points of a loop, but it is sufficient toapply the checking members to the loops of the natural vibrations thefrequencies of which are close to thoseof the overtones of singleconcentric zone.

the sounds to be reproduced. But for obtaining pure Vibrations thechecking members are preferably disposed symmetrically of the diaphragm,and where several natural vibrations overlap I provide stronger checkingmembers by providing comparatively thick wires or a plurality of thinwires. Ordinarily I have found that it is desirable not to apply morechecking members than is necessary for obtaining the result aimed at. Ihave found that in a circular diaphragm it is necessary to applychecking members to a The position of the zone to which the checkinmembers must be applied can be determined theoretically or byexperiment, for example by means of figures of sand produced on thediaphragm by vibration. In simple forms of diaphragms such as circulardiaphragms the said figures are known.

Where high checking power is needed several wires are disposed incontact with each other, so that the checking power is increased by thefrictional engagement of the checking members. By the said frictionalengagement objectionable noises are not produced by reason of thethinness of the wires.

Preferably the contacting checking members are different in form, as isshown in Fig. 3, in order that the members are differently coupled witheach other and the diaphragm is uniformly sensitive as to thecharacteristic high tones.

As appears from Fig. l the zone of the diaphragm which is acted upon bythe vibrating device f, g is as far as possible free of checkingmembers, the dimension of the said free zone being such that the naturalvibration of the said free zone is at least 3000 per second, and thedesired vibrations imposed on the diaphragm can be developed withoutbein checked.

It is important that the dimension of the checking members becomparatively small, and therefore the bottom of the box and the disk 0are disposed closely to the diaphragm. The distance between the saidsupporting members and the diaphragm should not be more than a smallfraction of a centimeter, and in the example shown in the figure it isfrom 12 millimeters. The radius of the curvature of the checking membersdepends on the said distance between the diaphragm and the support ofthe checking members, and therefore it is not more than a fewmillimeters. I

By disposing the checking members at opposite sides of the diaphragm, asis shown in Fig. 1, a uniform checking action is insured. In case oftransformation by pressure I dispose the checking member in the area ofthe transformation.

Therefore the arrangement of the check ing member is particularly simplein diaphragms for telephone receivers in which ordinarily asingle seriesof checking members is disposed concentrically of the center of thediaphragm,and on a circle dividing the radius of the diaphragm along thegolden section. Golden section as here employed is a geometrical termand signifies a bisection of the diameter of a circle such that onesection thereof is equal to the chord of a regular decagon inscribedwithin the circle. The relation may be expressed in the equation, z(r'w)=x in which ris the radius and w a section thereof. The relationcorresponds substantially to the division of a line on the ratio of 3:5.

The checking effect may be increased by disposing the said checkingmembers concentrically of the disk in a closed circle, and in this casethe effect is further increased by closing the circle of the checkingmembers as far as possible for example by inserting particularlyfinechecking members between the checking members of normal size. Inthis construction the checking action is supported by the obstruction oftlie'flow of air within the circle of checking members The checkingdevice has been described herein as applied to a sound reproducingapparatus in which the diaphragm is fixed at its margin to its carrier.But it may also be used in systems having freely supported diaphragms,in which case the checking members may be constructed for supporting thediaphragm.

Preferably the checking members are applied to loops of those overtonesof the natural vibration which are next to the fundamental. naturalvibration of the diaphragm.

The springs act as coupling members, and thus they act by theirvibration on the vibrations of the diaphragm.

Ordinarily the checking members are made from wire which may beirregularly crumpled or'bent into coils. But I wish it to be understoodthat I do not limit myself to these features and that checking membersmay be made from other elasticbodies such as bands.

Figs. 3 and 4 show some examples of pl" ting the checking membersbetween the diaphragm and their support. As shown at k the coils aresimply located with their axes parallel to the diaphragm, and some orall the windings of the coils are glued to the diaphragm. At k a coil isshown the axis of which is more or less perpendicular to the diaphragm,and at 7L3, k a pair of coils is shown which are combind into a singlechecking member, and which are in frictional engagement with each other.In Fig. 3 at m, m small bodies of material such as lacquer or glue areindicated, by which the coils k may be secured in position upon thediaphragm b. I have, however, explained above that such securingbodiesneed not in all cases be 'theform of bodies made from filaments ofhighly elastic metal engaging said diaphragm at some parts of thesurface thereof and leaving the other parts bare.

3. A sound reproducing device, comprising a diaphragm, means forvibrating said diaphragm in accordance with the sounds to be reproduced,and damping members in the form of bodies made from highly elastic hardfilaments engagin said diaphragm at the loops of the overtones of thenatural vibrations of the diaphragm and leaving the other parts bare.

4:. A sound reproducing device, comprising a diaphragm, means forvibrating said diaphragm in accordance with the sounds to be reproduced,and checking members in the form of wires of highly elastic material anda thickness of from 1/100 to 5/100 of a millimeter engaging saiddiaphragm at points permitting the overtones of the natu ral vibrationsof the diaphragm to be selectively checked.

5. A sound reproducing device, comprising a diaphragm, means forvibrating said diaphragm in accordance with the sounds to be reproduced,and damping members in the form of exceedingly fine bodies of highlyelastic hard material engaging said diaphragm at opposite sides and atsome points thereof and leaving the other parts bare, and rigidsupporting members for said clamping members located a small distanceaway from said diaphragm.

6. A sound reproducing device, comprising a diaphragm, means forvibrating said diaphragm in accordance with the sounds to be reproduced,and damping members in the form of bodies made from filaments of highlyelastic hard material engaging said diaphragm at some parts of thesurface thereof and leaving the other parts bare, and a rigid supportingmember for said damping members, the distance between said diaphragm andsaid supporting member being a small fraction of a centimeter.

7. A sound reproducing device, compris ing a diaphragm, means forvibrating said diaphragm in accordance with the sounds to be reproduced,and damping members in the form of bodies made from curved filaments ofhighly elastic hard material engaging said diaphragm at some parts ofthe surface thereof and leaving the other parts bare, the number, thethickness and the curvature of said filaments being such that theincrease of the amplitude of the vibration caused by the naturalvibration of the diaphragm in case of median oscillation is clampedthereby.

8. A sound reproducing device, comprising a diaphragm, means forvibrating said diaphragm in accordance with the sounds to be reproduced,and damping members in the form of bodies made fromhighly elastic hardfilaments engaging said diaphragm at some parts of the surface thereofandleaving the other parts bare, some of said damping members being infrictional engagement with each other and being so thin that obnoxiousnoises are not produced. 0,

9. A sound reproducing device, comprising a diaphragm clamped along itsmargin,

means for vibrating said diaphragm in accordanoe with sounds to bereproduced, and damping members in the form of bodies composed of curvedfilaments :of highly elastic hard material, the radius of the curvatureof said filaments being a small fraction of a centimeter.

10. A sound reproducing device, comprising a diaphragm, means forvibrating said diaphragm in accordance with the sounds to be reproduced,and damping members in the form of bodies made from filaments of highlyelastichard materials engaging said diaphragm along a narrowrzonedisposed concentrically of the diaphragm and dividing the radius of saiddiaphragm along the golden section.

11. A sound reproducing device, comprising a diaphragm, means forvibrating said diaphragm in accordance with the soundsto be reproduced,and damping members in the form of bodies made from tungsten filamentsengaging said diaphragm at some parts of the surface thereof and leavingthe other parts bare.

12. A sound reproducing device, comprising a diaphragm, means forvibrating said vdiaphragm in accordance with the sounds to bereproduced, and damping members in the form of bodies made from steelfilaments engaging said diaphragm at some parts of the isjurface thereofand leaving the other parts are.

13. A sound reproducing device, comprising a diaphragm, means forvibrating said diaphragm in accordance with the sounds to be reproduced,damping members disposed. concentrically of the diaphragm in 14; A soundreproducing device, con1prising a box having a closed bottom and nearlyclosed top, a diaphragm between said bottom and top, and damping membersengaging said diaphragm at the loops of the natural vibrations thereof.

15. A sound reproducing device including a plane-surfaced body, avibratory diaphragm extending in parallelism to the Y 5 plane surface ofsaid body and spaced at an interval from the plane surface thereof, and

a dampening member in the form of a helix of Wire arranged in thelnterval between the diaphragm and the body first named engaging thesurface of the diaphragm and the opposite plane surface of the bodyfirst named at opposite points and secured in such position. I

16.'The structure of claim 15, the helix being secured to the diaphragm.

17. A'sound reproducing device including a plane-surfaced body, avibratory diaphragm peripherally secured and extending in parallelism tothe plane surface of the body first named and at an interval from theplane surface of the body first named, means arranged opposite thediaphragm at a point Within its periphery for setting the diaphragm invibration, and means for dampening diaphragm vibration, such meansincluding a'plurality of helical springs arranged in the intervalbetween the plane surface of the body first named and the dia phragm andsecured in position at equal distances from that point in the extent ofthe Vibratory diaphragm opposite Which the vibratory means are situated.

18. A sound reproducing device comprising a diapl'iragm, means forvibrating said diaphragm in accordance With the sounds to be reproduced,and a dampening member in the form of a body made from a filament ofhighly elastic, hard material engaging said diaphragm in point contact.

In testimony whereof I hereunto aflix my signature.

DR. EMIL PODSZUS.

